Question

先化简在求值[2x(x^2y-xy^2)+xy(xy-x^2)]÷(x^2y),其中x=2008,y=2007

Answer 1

[2x(x^2y-xy^2)+xy(xy-x^2)]÷(x^2y)

=[2x*xy（x-y）+xy*x（y-x）]÷(x^2y)

=[2x^2*y(x-y)-x^2*y(x-y)]÷(x^2y)

=x^2*y(x-y)÷(x^2y)

=x-y

把x=2008,y=2007代入上式,得

[2x(x^2y-xy^2)+xy(xy-x^2)]÷(x^2y)

=x-y

=2008-2007

=1